May, 2025 - Mark Lynas

The good news is that we might be about to solve the Fermi paradox. Many have long suspected that the reason why there don’t seem to be millions of talkative aliens out there in space is because when an intelligent civilisation develops the technology to enable interstellar communication it also develops weapons that enable it to quickly destroy itself.

So far, we’re matching exactly this trajectory. We’ve sent probes far beyond the solar system – and vast quantities of electronic data fizzing in all directions at the speed of light – but we’ve also got thousands of thermonuclear weapons on hair-trigger alert that can in just a few hours reduce our entire world to a dark, freezing wasteland.

Whether or not we can confound the apparent inevitability of this doomsday outcome is perhaps the ultimate test of our species-level intelligence. But the omens aren’t good. Russia and the United States currently have 1,500 fully deployed nuclear warheads and over 5,000 each in their total arsenals. China is racing to reach nuclear parity by 2030. The current geopolitical instability raises the risk of superpower world war to perhaps the greatest level since the hottest periods of the Cold War.

America’s ‘launch-on-warning’ posture means that ICBMs (inter-continental ballistic missiles) must be out of their silos and in the air while the incoming missile attack is still blips on a radar screen. Once launched ICBMs cannot be recalled, nor can their targets be altered. When warning is received of imminent attack, the US president has as little as six minutes to decide whether to launch an all-out retaliation that would destroy most life on Earth.

A major thermonuclear exchange would likely kill about 770 million people in blasts and city firestorms across the major combatant powers. Technical language can obscure the reality here: this means several hundred million people – women, children, men, the elderly – being burned alive. Many more would quickly die from radioactive poisoning, but the biggest killer would come after: a decade-long worldwide nuclear winter that would starve billions more to death and wreck our civilisation beyond repair.

And all for what? Nothing matters this much; not any current-day flashpoint or contested piece of territory. The probability of nuclear war in any single year is small, probably around 1%, but this compounds to a two-thirds risk over a century. We have been extremely lucky with past near-misses, from Black Saturday of the Cuban Missile Crisis in 1962 to the notorious ‘3am phone call’ incident in 1980 when President Carter was nearly woken in the night when 2,200 incoming Soviet missiles were erroneously displayed on warning screens.

We would be unwise to trust to luck forever. It should be obvious that nuclear weapons and human civilisation cannot co-exist together long-term. Either we abolish them or they abolish us. To do so we will need to build a citizens’ movement singularly focused on the goal of total abolition. This will need to be very different from the anti-nuclear movements of the past: we can learn a huge amount from both the successes and failures of CND and other previous campaigns. Nor is it about abolishing nuclear power, which is a vital technology to tackle the climate crisis and can even help remove warheads from our world by burning them up as fuel.

Nor can we be unilateralist, because the process can only work via simultaneous trust-building disarmament by all the nuclear nations. This new movement must involve millions of people of all political persuasions in every country of the world whose only reason for participation is that they want to survive. We have a good head start in the 2017 UN Treaty on the Prohibition of Nuclear Weapons, already signed by 93 countries. In other words, almost half the world’s nations are now on board with the drive towards abolition.

This should be an easy decision. Collective suicide is in nobody’s interest. We don’t need to burn alive millions of men, women and children, and usher in a nuclear winter that destroys the biosphere. But the first step is to break out of the fatalistic denial that views nuclear weapons as inevitable and the aim of abolishing them as impossible. That way the Fermi paradox can remain unanswered, and humanity can continue to flourish on our beautiful, living planet.

For the full published version see the NewScientist magazine.

By Mark Lynas and Ted Nordhaus

First published in the Wall Street Journal, 15 May 2025

The world is on the brink of a climate apocalypse—not one caused by gradual greenhouse emissions but by a sudden exchange of nuclear weapons, a possibility made more salient by the current conflict between India and Pakistan. While the long-term effects of emissions are uncertain, we know that a nuclear war would result in an immediate nuclear winter.

When we think about nuclear apocalypse, we tend to think of the immediate effects: thermonuclear explosions that incinerate cities and vaporize populations. But the worst consequences unfold long after the weapons have detonated. A major thermonuclear exchange would shroud the atmosphere in soot, plunging the world into darkness and ushering in a decadelong winter. While hundreds of millions of people would likely be killed in the initial conflagrations, most of the human population—including those in the combatant nations—would likely die in the subsequent winter famine.

It’s comforting to think that an exchange of nuclear warheads in a regional conflict such as that between India and Pakistan might be more limited. The death toll from the detonation of a few dozen weapons might only number in the low millions, and there would be little effect on planetary temperatures.

But if India bombed Islamabad and Pakistan bombed Mumbai in retaliation, it would be hard to prevent further escalation. Moreover, once intercontinental ballistic missiles are in the air, it’s virtually impossible for other nuclear-armed nations to determine where they’re headed. Leaders in Washington, Moscow and Beijing would need to make decisions in a matter of minutes about whether to launch their own weapons.

Midrange scenarios involving a few hundred weapons would cool the climate enough to decimate global food production and trade and would likely kill hundreds of millions.

Under worst-case scenarios, droughts and crop failures would quickly spread across the globe. Hundreds of millions of refugees would cross continents in search of food, safety and shelter. Some would die of disease and illness, most of starvation. Human civilization would be over.

In comparison, there’s no conceivable global-warming scenario that would kill off most of the world’s population in only a few years. Climate change damages natural systems such as coral reefs and the Arctic and will increasingly stress human societies, but it’s not an existential risk akin to nuclear war.

Unless we reduce and ultimately eliminate greenhouse gas emissions, global temperatures will continue to rise. Climate change could also lead to abrupt changes in earth’s ecosystems, such as irreversible melting of the ice sheets in Greenland and Antarctica. While these changes will be fast on geological time scales, they’ll be slow on human time scales, unfolding over decades and centuries. Humanity will have time to adapt food production to climate change and become more resilient to extreme weather and sea-level rise. We also have many available off-ramps, from nuclear energy to solar geoengineering, that can limit future warming.

Nuclear winter, by contrast, would destroy civilization beyond repair within months or years. Yet unlike climate change, which has preoccupied activists for decades, it is largely ignored. Politicians, journalists and activists don’t travel by the tens of thousands every year to attend conferences on the threat of nuclear annihilation. Philanthropists such as Bill Gates and Jeff Bezos don’t spend billions on efforts to eradicate the threat. There’s no nuclear equivalent to Greta Thunberg lecturing the United Nations General Assembly about its failure to assure our survival. The antinuclear movement has bizarrely focused on eliminating clean power-generating nuclear reactors instead of city-incinerating nuclear weapons.

Arguably, President Trump is the most prominent figure warning of nuclear war, with his frequent invocations of World War III. Mr. Trump was also an advocate for arms control in the 1980s.

The arms control regime that world leaders painstakingly built during the latter stages of the Cold War is in tatters. The New Strategic Arms Reduction Treaty (New START), an accord signed in 2010 that limits Russia and the U.S. to 1,550 deployed warheads each—still plenty to destroy civilization—expires next February. Russia and the U.S. each hold more than 5,000 additional warheads in reserve. China, meanwhile, is rapidly building its nuclear inventory.

Against this backdrop of rising economic and geopolitical instability, the contrast is stark between the genuinely existential—but largely ignored—threat of nuclear warfare and the immense amount of attention and political effort lavished on the climate issue. Climate change is real, and there’s much that we can and should do about it. But nuclear war is the far more imminent threat.

Whatever else one thinks about the current administration’s novel approach to longstanding geopolitical alliances, President Trump deserves some credit for pushing Russia and Ukraine to agree to a cease-fire and appears to have played a significant role in brokering a cease-fire between India and Pakistan over the weekend.

Conflicts between nuclear-armed adversaries remind us that no other risk to human societies remotely rivals nuclear warfare. Zero nuclear weapons may be as much a pipe dream as net zero, but there should be no higher priority for politicians, philanthropists and civil society leaders, whatever their political stripe, than to de-escalate that threat.

Mr. Nordhaus is director of the Breakthrough Institute. Mr. Lynas is author of “Six Minutes to Winter: Nuclear War and How to Avoid It.”

Mark Lynas

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